Clutch device for a hydrostatic continuously variable transmission

Abstract

In a hydrostatic continuously variable transmission, a hydraulic pump is linked to a hydraulic motor by a hydraulic closed circuit to change the capacity of the hydraulic motor so as to change the speed of a motorcycle continuously. A clutch device comprising a clutch valve for connecting and disconnecting a high pressure side oil passage and a low pressure side oil passage constituting the hydraulic closed circuit. A governor mechanism for generating governor force corresponding to the input rotation speed of the hydraulic pump and applying this governor force in the closing direction of the clutch valve. A spring for giving urging force in the opening direction of the clutch valve, and a buffer mechanism having a variable oil chamber and an oil pool chamber for easing the opening and closing movements of the clutch valve activated according to the governor force and the urging force.

1. A hydrostatic continuously variable transmission comprising:
 a fluid pump and a fluid motor linked together in a closed circuit, wherein the capacity of at least one of the pump or the motor is variable to enable control of the relative rotational speeds of a pump input and a motor output, wherein the pump is a hydraulic pump, the motor is a hydraulic motor, and the fluid is a hydraulic fluid, 
 a clutch device for engaging or disengaging force transmission between the pump and the motor, the clutch comprising:
 a clutch valve that can be opened to connect a high pressure fluid passage with a low pressure fluid passage of the closed circuit, or closed to disconnect the high pressure fluid passage from the low pressure fluid passage of the closed circuit; 
 a mechanism constructed to generate a force in a closing direction of the clutch valve in response to the rotational speed of the pump input, wherein the mechanism constructed to generate a force in the closing direction is actuated by centrifugal force generated by the input rotation; 
 a mechanism constructed to dampen the opening and closing of the clutch valve, 
 wherein the clutch valve includes a valve spool that is movably arranged in a spool hole formed in the axial direction of a support shaft. 
 
 
     
     
       2. The transmission according to  claim 1 , wherein the pump is of a fixed capacity type having a predetermined cam plate angle, and the motor is of a variable capacity type having a variable cam plate angle and a motor servo mechanism for changing the angle of the motor cam plate. 
     
     
       3. The transmission according to  claim 1 , wherein the transmission further comprises a lock-out mechanism for maintaining a constant relative rotational speed of a pump input and a motor output. 
     
     
       4. The transmission according to  claim 1 , wherein the mechanism includes weights that displace radially outward for applying a force in the closing direction of the clutch valve. 
     
     
       5. The transmission according to  claim 1 , wherein the mechanism constructed to apply a force in the opening direction includes a spring. 
     
     
       6. The transmission according to  claim 1 , wherein the mechanism constructed to dampen the opening and closing of the clutch valve includes:
 a variable hydraulic chamber; and 
 an oil pool chamber, the oil pool chamber being in fluid communication with the variable hydraulic chamber such that the movement of the clutch valve is dampened by the resistance due to fluid flow between the variable hydraulic chamber and the oil pool chamber. 
 
     
     
       7. The transmission according to  claim 6 , wherein the dampening effect is increased or decreased according to a restriction of a fluid flow between the variable hydraulic chamber and the oil pool chamber. 
     
     
       8. A clutch device for a hydrostatic continuously variable transmission, the hydrostatic continuously variable transmission being constituted such that a hydraulic pump and a hydraulic motor are linked together by a hydraulic closed circuit, and the capacity of at least one of the hydraulic pump or the hydraulic motor is controlled to change the ratio of an input rotation of the hydraulic pump and an output rotation of the hydraulic motor,
 the clutch device comprising:
 a clutch valve for connecting and disconnecting a high pressure side oil passage and a low pressure side oil passage which constitute a part of the hydraulic closed circuit, to control the transmission of rotation from the hydraulic pump to the hydraulic motor; 
 a governor mechanism for generating governor force corresponding to the input rotation speed of the hydraulic pump, wherein centrifugal force generated by the input rotation of the hydraulic pump is used by the governor to apply a force in the closing direction of the clutch valve; 
 urging means for applying an urging force in the opening direction of the clutch valve; and 
 a buffer mechanism for easing the opening and closing movements of the clutch valve activated according to the governor force and the urging force, 
 wherein the clutch valve includes a valve spool that is movably arranged in a spool hole formed in the axial direction of a support shaft. 
 
 
     
     
       9. A clutch device for a hydrostatic continuously variable transmission, the hydrostatic continuously variable transmission being constituted such that a hydraulic pump and a hydraulic motor are linked together by a hydraulic closed circuit, and the capacity of at least one of the hydraulic pump or the hydraulic motor is controlled to change the ratio of an input rotation of the hydraulic pump and an output rotation of the hydraulic motor,
 the clutch device comprising:
 a clutch valve for connecting and disconnecting a high pressure side oil passage and a low pressure side oil passage which constitute a part of the hydraulic closed circuit, to control the transmission of rotation from the hydraulic pump to the hydraulic motor; 
 a governor mechanism for generating governor force corresponding to the input rotation speed of the hydraulic pump, wherein centrifugal force generated by the input rotation of the hydraulic pump is used by the governor to apply a force in the closing direction of the clutch valve; 
 urging means for applying an urging force in the opening direction of the clutch valve; and 
 a buffer mechanism for easing the opening and closing movements of the clutch valve activated according to the governor force and the urging force, 
 wherein the clutch valve includes a valve spool that is movably arranged in a spool hole formed in the axial direction of a support shaft, the shaft being constructed to rotatably support the hydraulic pump and the hydraulic motor, the valve spool arranged in the spool hole such that the high pressure side oil passage and the low pressure side oil passage are connected or disconnected according to the movement of the valve spool in the spool hole; and 
 wherein the buffer mechanism has a variable oil chamber which is surrounded by the inner wall of the spool hole and the outer wall of the valve spool and whose capacity is changed by the movement of the valve spool and an oil pool chamber which is connected to the variable oil chamber and formed in the valve spool. 
 
 
     
     
       10. The clutch device according to  claim 9 , wherein an oil passage having an orifice connected to the oil pool chamber is formed in the valve spool for discharging oil from the variable oil chamber to the oil pool chamber to provide resistance to a change in the capacity of the variable oil chamber and to ease the movement of the valve spool. 
     
     
       11. The clutch device according to  claim 10 , wherein the oil passage is formed in the valve spool so as to be open to a connection portion for connecting the governor mechanism with the valve spool. 
     
     
       12. A hydrostatic continuously variable transmission comprising:
 a fluid pump and a fluid motor linked together in a closed circuit, wherein the capacity of at least one of the pump or the motor is variable to enable control of the relative rotational speeds of a pump input and a motor output, 
 a clutch device for engaging or disengaging force transmission between the pump and the motor, the clutch comprising:
 a clutch valve that can be open to connect a high pressure fluid passage with a low pressure fluid passage of the closed circuit or closed to disconnect the high pressure fluid passage from the low pressure fluid passage of the closed circuit; 
 a means for generating a force in a closing direction of the clutch valve in response to the rotational speed of the pump input, 
 a means for dampening the opening end closing of the clutch valve, 
 wherein the clutch valve includes a valve spool that is movably arranged in a spool hole formed in the axial direction of a support shaft.